Transducer assembly



June 9,1959 P. N. LEHR TRANSDUCER ASSEMBLY 2 Sheets-Sheet l Filed Oct.10, 1956 m T w W.

PHILIP N. LEHR his ATTOR r am NEYS

June 9,1959 P, NLEHR 2,890,297

TRANSDUCER ASSEMBLY Filed Oct. 10, 1956 2 Sheets-Sheet 2 INVENTOR.PHILIP N. LEHR r ATTORNEYS United States Patent TRANSDUCER ASSEMBLYPhilip N. Lehr, Huntington, N.Y., assignor to Dictograph ProductsCompany, Inc., Jamaica, N.Y., a corporation of Delaware ApplicationOctober 10,1956, Serial No. 615,107

4 Claims. 01. 119-119 This invention relates to transducer assembliesfor reproducing or responding to acoustic energy. More particularly, itrelates to small transducer assemblies for operating rather close to theuser under difficult conditions such asmight be encountered, forexample, in the case of a. hospital patient speaking through orlisteningto the transducer while it is supported on or near the bed.

Portable transducer assemblies for use in or about beds tend to belimited in their performance characteristics due to such factors as sizelimitation, the necessity of withstanding abuse, and the likelihood ofmufiling by the bedding. Thus the assemblies must be compact andpreferably of light weight; they must the robust in cou' structio-n;and, if they are to be wholly useful, must be capable of reproducing orresponding to a reasonable range of frequencies even when partiallysmothered in the bedding. Preferably, they should be capable ofoperation both to reproduce sounds for the patient to hear, 'such asmusic or instructions, and, selectively, to reproduce the sounds by thepatient for the ears of a centrally located nurse, for example. In thelatter case, the trans: ducer assemblies should be capable of achievingat least someresponse to sounds, no matter how theassemblies mightbeoriented with respect to' the sound source.

In accordance with the present-invention, therefore, there is provided atransducer assembly including a pair of companion housing parts each ofgenerally dished conrelatively soft compliant surface such as a pillowwith relatively little possibility of all ports being blocked.Furthermore, the sizes and numbers of the ports communicating with theclosed chamber and the front of the speaker can be so arranged thatreinforcement occurs in: the bass frequency range of the speaker,thereby to extend its range, while at the same time presenting access tothe cone from all directions.

The speaker can be mounted within the chamber defined by the companionhousing parts with its mouth portion engaging the insideface of thefront part and with its magnet or driver portion engaging the insideface of the back part, thereby bridging the distance therebetween. Also,complementary recesses can be provided in the margins of the companionhousing pieces to receive fixedly the end sleeve or molding of anelectrical cord.

. 'A' representative embodiment of the invention from figuration andformed of a tough durable material. The

parts are brought together with their respective concave surfaces inopposition to define-a shallowfully enclosed chamber for receiving thetransducer, commonly called the speaker, across its depth. The fronthousing part-includes a central gently rounded portion pierced by acluster of ports or openings which pass acoustic energy directly to orfrom the speaker cone. Beyondthis' central area and beyond the mouth ofthecone, radially speaking, are another series of ports whichcommunicate with the chamber and hence with the back surface of the conein the manner of bass reflex enclosures.

The back housing part is formed with a'flat central supporting surfaceon which the assembly can rest, as

ports in larger speaker on a pillow, for example, with the portionsbeyond the 1 supporting surface tapering rather steeply toward the edgeswhich abut the front housing part. Formed in the tapering portion wellspaced from the flat surface, are a series of ports which alsocommunicate with the closed chamber and hence the back surface of thespeaker cone.

which, the above and other features will be readily understood by thoseskilled in the art is described below having reference to theaccompanying drawings in which:

, Figure 1 is a front view of a transducer assembly;

' Figure 2 is a view in vertical section taken on the line 2-2 of Figure1 looking in the direction of the arrows; Figure 3 is a back View of theassembly of Figure l; and

Figure 4 is a view in transverse section taken on the line i 4 of Figure3, looking in the direction of the arrows.

Referring to the drawings, the invention is illustrated as embodied in atransducer assembly indicated generally by the numeral 10 and comprisedof a pair of companion housing parts including a front part 11 ofgenerally dished configuration with its convex surface facing outwardlyand, edgewise abutted thereto and secured as by cementing or detachablefasteners (not shown) a back part '12 also of dished configuration andhaving its convex surface facing outwardly. The housing parts 11 and 12are preferably formed from a tough, durable material such as plastic,all exposed surfaces being free of pronounced irregularities orprojections which might become fouled in the bedding or cause discomfortor injury to the user.

The 'abutting edges of the two housing parts are preferably held toclose tolerances during fabrication to insure a tight fit, and suitableshoulders are included to prevent relative lateral displacement.

The mated housing parts 11 and 12 define a closed chamber 13 across themaximum depth of which extends atransduce'r in the form of a loudspeaker 14 having its mouth ring 14a abutting or, if desired, secured tothe inside surface 11a of the front housing part 11 and its rear-mostframe part, the latter taking the form of a magnet 14b, attached as byscrews 15 to the inside face 12a of the backhousing part 12. Thediameter of the speaker 14 at its largest point is smaller than thediameter of the front housing part 11 so that the chamber 13 extendsradially beyond the limits of the speaker 14.

The face of the front housing part 11 is formed with a dense cluster ofports or openings 16 all disposed within the area circumscribed by themouth 14a of the speaker 14. Thus, acoustic energy from or to the frontof the speaker cone or diaphragm 14c, nested within a spider or frame14a, passes only through the openings 16. Also formed in the front faceof the housing part 11 are a 5 series of openings 17 communicating withthat portion of the chamber 13 which is outside the confines of thespeaker mouth 14a, the openings 1'! in the illustrated embodiment beingarranged circumferentially-about the 3 speaker axis on a radius largerthan that of the speaker mouth.

The back or rear housing part 12, as best seen in Figure 3, is formedwith a generally flattened surface 12a on which the speaker can rest andto which, as described, magnet 14b can be bolted. So arranged, it willbe seen that the mated housing parts 11 and 12, being secured to thefront and back, respectively, of the speaker, augment the framework ofthe speaker, including the spider, for example, thereby reducingresonances. If desired, a name plate or other suitable indicating meanscan be affixed to the flat back surface of the back housing part 12,this surface serving also as a support on which the transducer assemblycan be rested. Surrounding the flat center portion of the back housingpart 12 is a curving portion 12b tapering toward the outside perimeterof the housing assembly. Formed in the tapering portion 12b at pointsclose to the outermost extremes of the chamber 13 radially speaking area series of ports or openings 18. Both the openings 17 in the fronthousing part 11 and the openings 18 in the back housing part 12 arearranged to pass acoustic energy to or from the back of the cone 14c ofthe speaker 14. It will be observed that the number of openings 16accommodating acoustic energy to or from the front of the cone 14cgreatly exceed the number which accommodate energy to or from the backof the cone. The relative areas of the openings 16, 17 and 18, theinherent performance characteristics of the speaker 14, the size of thechamber 13, and the natural resonances of the housing parts 11 and 12are such that a reflex principle obtains which greatly improves the baseresponse of the assembly. In view of the over-all size of the assembly,which can be approximately five inches in diameter and two inches inthickness, the frequency range, particularly in the lower limits, hasbeen found to exceed that normally obtainable with assemblies ofcommensurate size.

The assembly is adapted to be operated without any appreciable loss inefiiciency when resting on very compliant surfaces such as pillows. Atthe most, some or all of the openings 18 might become blocked by thepillow. In these circumstances, both the direct radiation openings 18and the reflex openings 17 can operate. In other positions 'in thebedding, larger percentages of the openings 16, 17 and 18 might becomeblocked. Regardless of how the assembly is disposed among the bedding,however, it is unlikely that all of the openings16, 17 and 18 willbecome fully blocked, so that at least some energy can pass to or fromthe speaker. Also, because the speaker unit 14 is rigidly securedbetween the mated housing parts, the housing itself can be utilized toradiate limited amounts of acoustic energy.

Because so-called pillow speakers are often used to convey messages topatients in hospital beds through an intramural communication system, aswell as to transmit sounds from the patient back to a nurses desk, forexample, it is important that the speaker assembly not be renderedcompletely inoperative by the bedding. A speaker closure formed inaccordance with the present invention can conveniently be hung at thebedside, as on the bed head, for example, or it can be rested front faceup on the pillow beside the patient, with good acoustic effects.

The front and back housing parts 11 and 12 can be formed with opposingrecesses 19 and 20 to receive a molded plug member 21 at the terminalend of anelectrical cord 22. Preferably, plug 21 is tightly secured tothe housing as by set screw 23, for example, to prevent inadvertentdetachment in the event of rough handling.

While the invention has been described above having reference to apreferred embodiment thereof as illustrated in the drawings, it will beunderstood that it can take various forms and shapes without departingfrom the spirit of the invention. The invention should not, there- 4fore, be regarded as limited, except as defined by the accompanyingclaims.

Iclaim:

1. In a small, portable transducer assembly, a housing having atransducer chamber therein, a first port means in the front face of thehousing, a second port means in the front face of the housing arrayedabout the first port means, means to mount a transducer in the cavityfacing the first port means, said second port means communicating withthe cavity beyond the front face of the transducer, third port means inthe back face of the housing communicating with the cavity, said secondand third port means having a total port area which is considerably lessthan the port area of the first port means, said housing being generallyconvexly rounded with the marginal portions of the back face convergingtoward the marginal portions of the front face, and said third portmeans being formed in the marginal portions of the back face.

2. A small portable transducer housing assembly particularly adapted foruse in and about beds, comprising a generally convexly rounded housingflattened in profile, and generally circular in full face projection,said housing having an internal cavity defined by a pair of generallyflattened opposing inner surface portions flanked by convergent wallportions which meet near the periphery of the housing, a transducercentrallymounted in the cavity to bridge the distance between saidflattened inner surface portions and being supported at its oppositeends, said transducer including a diaphragm facing the inside of thefront face of the housing and a base portion facing the inside of theback face of the housing, a cluster of first ports piercing the frontface of the housing and communicating exclusively with the forwardlyfacing surface of the diaphragm, a series of second ports piercing thefront face of the housing and communicating with the cavity, therebycommunicating with the back surface of the diaphragm when the housing isin use, a series of third ports piercing the back surface of the housingand communicating with the cavity and the back surface of the diaphragm,and said third ports being formed in the convergent wall portions of thehousing, whereby the assembly can be rested on a supporting surface,back face down, without blocking the third ports.

3. A small portable transducer housing assembly particularly adapted foruse in and about beds, comprising a generally convexly rounded housingcircular in full face projection and flattened in profile, said housingcomprising dished front and rear housing portions of generally the samesize and configuration joined at their peripheries with their concavesurfaces opposing one another to define an internal cavity, saidopposing inner surfaces including generally flattened central portionsand converging marginal portions, a transducer mounted in the cavity andincluding a vibratable conical diaphragm abutted against the flattenedportion of the inner surface of the front housing portion and anelectromagnetic driver coupled to the diaphragm and secured at its backportion to the flattened inner surface of the rear housing portion, acluster of first ports piercing the flattened portion of the fronthousing portion and communicating with the forwardly facing surface ofthe conical diaphragm, a series of second ports piercing the frontsurface of the housing portion and circumferentially arrayed about thecluster of first ports and communicating with the cavity outside theperipheral limits of the conical diaphragm, thereby communicating withthe backsurface of the diaphragm within the cavity, and a series ofthird ports piercing the converging marginal portions of said rearhousing and communicating with the cavity and hence the back surface ofthe diaphragm, said second and third ports having a total port areawhich is considerably less than the total port area of the first ports.

4. A transducer assembly as set forth in claim 2, said transducerincluding a spider frame supporting the conical diaphragm, the spiderframe being supported at its forward portion by the front housingportion and at its rearward portion by the base of the transducer and bythe back housing portion, whereby the housing reinforces the spiderframe to suppress resonances.

References Cited in the file of this patent UNITED STATES PATENTSKettler July 15, 1952

